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// -*- mode:doc; -*-
// vim: set syntax=asciidoc:
[[toolchain]]
Cross-compilation toolchain
---------------------------
A compilation toolchain is the set of tools that allows you to compile
code for your system. It consists of a compiler (in our case, +gcc+),
binary utils like assembler and linker (in our case, +binutils+) and a
C standard library (either
http://www.gnu.org/software/libc/libc.html[GNU Libc],
http://www.uclibc.org/[uClibc] or
http://www.musl-libc.org/[musl]).
The system installed on your development station certainly already has
a compilation toolchain that you can use to compile an application
that runs on your system. If you're using a PC, your compilation
toolchain runs on an x86 processor and generates code for an x86
processor. Under most Linux systems, the compilation toolchain uses
the GNU libc (glibc) as the C standard library. This compilation
toolchain is called the "host compilation toolchain". The machine on
which it is running, and on which you're working, is called the "host
system" footnote:[This terminology differs from what is used by GNU
configure, where the host is the machine on which the application will
run (which is usually the same as target)].
The compilation toolchain is provided by your distribution, and
OpenADK has nothing to do with it (other than using it to build a
cross-compilation toolchain and other tools that are run on the
development host).
As said above, the compilation toolchain that comes with your system
runs on and generates code for the processor in your host system. As
your embedded system has a different processor, you need a
cross-compilation toolchain - a compilation toolchain that runs on
your _host system_ but generates code for your _target system_ (and
target processor). For example, if your host system uses x86 and your
target system uses ARM, the regular compilation toolchain on your host
runs on x86 and generates code for x86, while the cross-compilation
toolchain runs on x86 and generates code for ARM.
OpenADK provides only one solution for the cross-compilation toolchain.
The versions for binutils, gcc, gdb and libc are fixed. It is a combination
of mostly the latest versions, which are known to work in this combination
and are known to produce usable firmware images. You normally do not need to
know the deep details, it is part of OpenADK policy to keep this part
simple for the user.
You can only choose between three C libraries:
http://www.uclibc.org[uClibc], the
http://www.gnu.org/software/libc/libc.html[glibc] and
http://www.musl-libc.org[musl].
There are some minimal configuration options provided in +Toolchain settings+.
You can enable or disable the building of following components and toolchain
options:
* GDB (enabled by default)
* GNU C++ compiler (enabled by default, when disabled
will prevent some packages to show up in the menu selection)
* Stack Smashing Support (SSP) support for GNU C/C++ Compiler (experimental, some packages will fail to build)
* Link Time Optimization (LTO) support for GNU C/C++ Compiler (experimental, some packages will fail to build)
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